A cannula or trocar tube is typically used in laparoscopic surgery to be inserted into and line an opening made in the body. In other words, a cannula provides a portal into a region within the body, such as the abdominal region, for example. A surgical trocar is a sharp pointed instrument typically initially inserted into a cannula with its pointed tip extending outwardly from a distal end of the cannula. The sharp tip facilitates penetration of the tissue of the body and positioning of the distal end of the cannula into the desired portion of the body. The trocar may be removed and a surgical instrument or endoscope may be inserted into and manipulated while extending through the cannula.
To increase visibility and instrument access within the body, a pressurized gas is typically introduced into the body to define a surgical cavity into which one or more cannulas may extend. Accordingly, the cannula typically requires a seal against a loss of pressurized gas both when no instrument is positioned within the cannula, and also when an instrument is positioned in the cannula. In addition, it may also be desirable to ensure a good gas seal with a shaft of the instrument even as the instrument is manipulated longitudinally into or out of the cannula, or as the instrument is moved in a lateral or side-to-side motion.
One conventional approach to sealing an instrument passageway through a cannula when no instrument is present provides a flapper valve within the upper end or cap of the cannula. For example, U.S. Pat. No. 5,104,383 to Shichman discloses a flapper valve with a raised center portion for effecting sealing with a valve seat defined by a valve mounting portion, and with the flapper being pivotally mounted to the surrounding mounting portion by a pivot pin. Along these lines, U.S. Pat. No. 5,290,245 to Dennis discloses a flapper valve including a domed valve plug, a bias spring for biasing the flapper to the closed position, and a hinge pin for pivotally connecting the flapper to an adjacent mounting portion.
U.S. Pat. No. 5,364,372 to Danks et al. discloses a flat flapper valve connected via a pivot pin and including a bias spring and associated lever arm. U.S. Pat. No. 5,411,483 to Loomas et al. also discloses a spring-loaded flapper valve having a flat flap portion. U.S. Pat. No. 5,385,553 to Hart et al. and No. 5,385,560 to Wulf also disclose conventional flat flapper valves oriented at an inclined angle and pivotally connected to the surrounding cap structure. Unfortunately, conventional flapper valves as have been used to seal a cannula require several individual parts which are typically independently manufactured and which are then assembled, such as by precise alignment and insertion of the relatively small hinge pin through the flapper and mounting openings to form the flapper valve.
Relating to the instrument entrance seal of a cannula, elastomeric materials have been used in a cannula cap to permit an instrument to pass through a suitable opening in the elastomeric material and while forming a seal with the instrument. For example, U.S. Pat. No. 5,330,437 to Durman discloses an elastomeric self-sealing valve having an undersized outer opening. U.S. Pat. No. 5,380,288 to Hart et al. discloses an outer seal that permits movement while an inner seal is more rigid to effect complete sealing.
U.S. Pat. No. 5,411,483 to Loomas et al., discussed briefly above, discloses various seal embodiments including an annular corrugated portion or bellows for facilitating lateral movement of an instrument at the outer seal of a cannula cap. Unfortunately, the cannula cap and bellows disclosed in the Loomas et al. patent, for example, includes a multiplicity of individual component parts requiring assembly. In particular, the seal disclosed in the Loomas et al. patent is mounted to a ring, in turn, which is captured for lateral movement by a pair of opposing walls.
In addition to mechanical and assembly complexity of many conventional cannula caps, the manufacturing costs for such caps can be relatively high. Accordingly, the relatively expensive cannula caps are desirably sterilized to permit multiple uses. However, in view of small pockets and other areas within the caps, sterilization of complicated components may also be relatively difficult.